How to remove duplicated e-mails in O365

Question

How can I easily remove duplicate e-mails across multiple folders when using O365

Answer 1

None of the Outlook versions have an option to remove duplicates. You can group by subject and delete the duplicates (if all in the same folder) or use a 3rd party utility. Most of the utilties work with classic Outlook, not web or new Outlook. I have a list of utilties on my website at https://www.slipstick.com/addins/duplicates-addins/duplicate-remover-tools-for-outlook/

If you are using classic and are using PST files or a Microsoft exchange account, you could export to a PST and don't export duplicates. This will only work if the dupes are in the same folder though. After exporting, then delete the messages from the exchange mailbox and import. If you exported from a pst, you can use the new PST as your data file and remove the one that had duplicates or delete all the mail and import the pst.

Disclaimer:

slipstick.com is a site I run as a Microsoft MVP and the content is much more accurate and relevant than a general internet search. While the site is in English, there are translations options under the search box.

Answer 2

To remove duplicate emails in Office 365, you can follow these general steps:

1. Identify Duplicate Emails: Use a third-party tool or Outlook's built-in features to identify duplicates. Some tools can automatically detect and manage duplicates across multiple folders.
2. Manual Removal: If you prefer to do it manually, you can go through your folders and delete duplicates one by one. This can be time-consuming, especially if you have many emails.
3. Use MFCMAPI: For a more technical approach, you can use MFCMAPI to identify and delete duplicate folders or items. This involves:
   • Downloading and running MFCMAPI.
   • Logging into your mailbox and identifying duplicate folders.
   • Copying items from duplicate folders to the original ones and then deleting the duplicates.
4. Backup Your Data: Before proceeding with any deletion, ensure that you back up your Outlook data or confirm that your Exchange Server mailbox is backed up to prevent data loss.
5. Consider Migration Issues: If you are migrating from another email service (like Gmail), be aware that duplication can occur due to how emails are organized in labels and folders. Make sure to exclude certain folders during migration to avoid this issue.

By following these steps, you can effectively manage and remove duplicate emails in your Office 365 environment.

---

References:

• Items reappear in a user's mailbox or are duplicated in the archive mailbox when an archiving policy is enabled during IMAP migration
• Troubleshooting issues with IMAP mailbox migration